Antenna with multiple coupled regions

ABSTRACT

An antenna having a driven element coupled to multiple additional elements to resonate at multiple frequencies. A magnetic dipole mode is generated by coupling a driven element to a second element, and additional resonances are generated by coupling additional elements to either or both of the driven or second element. One or multiple active components can be coupled to one or more of the coupled elements to provide dynamic tuning of the coupled or driven elements.

FIELD OF THE INVENTION

The present invention relates generally to the field of wireless communication. In particular, the present invention relates to antennas and methods of improving frequency response and selection for use in wireless communications.

BACKGROUND OF THE INVENTION

Commonly owned U.S. Pat. Nos. 6,677,915 filed Feb. 12, 2001, titled “SHIELDED SPIRAL SHEET ANTENNA STRUCTURE AND METHOD”; 6,906,667 filed Feb. 14, 2002, titled “MULTIFREQUENCY MAGNETIC DIPOLE ANTENNA STRUCTURES FOR VERY LOW PROFILE ANTENNA APPLICATIONS”; 6,900,773 filed Nov. 18, 2002, titled “ACTIVE CONFIGUREABLE CAPACITIVELY LOADED MAGNETIC DIPOLE”; and 6,919,857 filed Jan. 27, 2003, titled “DIFFERENTIAL MODE CAPACITIVELY LOADED MAGNETIC DIPOLE ANTENNA”; describe an Isolated Magnetic Dipole (IMD) antenna formed by coupling one element to another in a manner that forms a capacitively loaded inductive loop, setting up a magnetic dipole mode, the entire contents of which are hereby incorporated by reference. This magnetic dipole mode provides a single resonance and forms an antenna that is efficient and well isolated from the surrounding structure. This is, in effect, a self resonant structure that is de-coupled from the local environment.

The overall structure of the IMD antenna can be considered as a capacitively loaded inductive loop. The capacitance is formed by the coupling between the two parallel conductors with the inductive loop formed by connecting the second element to ground. The length of the overlap region between the two conductors along with the separation between conductors is used to adjust the resonant frequency of the antenna. A wider bandwidth can be obtained by increasing the separation between the conductors, with an increase in overlap region used to compensate for the frequency shift that results from the increased separation.

An advantage of this type of antenna structure is the method in which the antenna is fed or excited. The impedance matching section is almost independent from the resonant portion of the antenna. This leaves great flexibility for reduced space integration. The antenna size reduction is obtained in this case by the capacitive loading that is equivalent to using a low loss, high dielectric constant material. At resonance a cylindrical current going back and forth around the loop is formed. This generates a magnetic field along the axis of the loop which is the main mechanism of radiation. The electrical field remains highly confined between the two elements. This reduces the interaction with surrounding metallic objects and is essential in obtaining high isolation.

The IMD technology is relatively new, and there is a need for improvements over currently available antenna assemblies. For example, because cell phones and other portable communications devices are moving in the direction of providing collateral services, such as GPS, video streaming, radio, and various other applications, the demand for multi-frequency and multi-band antennas is at a steady increase. Other market driven constraints on antenna design include power efficiency, low loss, reduced size and low cost. Therefore, there is a need in the art for antennas which exceed the current market driven requirements and provide multiple resonant frequencies and multiple bandwidths. Additionally, there is a need for improved antennas which are capable of being tuned over a multitude of frequencies. Furthermore, there is a need for improved antennas which are capable of dynamic tuning over a multitude of frequencies in real time.

SUMMARY OF THE INVENTION

This invention solves these and other problems in the art, and provides solutions which include forming additional capacitively loaded inductive loops by adding additional elements that couple to one of the two elements that form the basic IMD antenna. Other solutions provided by the invention include active tuning of multiple coupling regions, switching over a multitude of frequencies, and dynamic tuning of resonant frequencies.

In one embodiment, an antenna is formed by coupling a first element to a second element, and then adding a third element which is coupled to the second element. The first element is driven by a transceiver, with both the second and third elements connected to ground. The additional resonance that is generated is a product of two coupling regions on the composite antenna structure.

In another embodiment, an antenna is formed having a first element driven by a transceiver, and two or more grounded elements coupled to the first element. The space between each of the two or more grounded elements and the first element defines a coupling region, wherein the coupling region forms a single resonant frequency from the combined structure. The resonant frequency is adjusted by the amount of overlap of the two elements. The separation between the two elements determines the bandwidth of the resonance.

In another embodiment, an antenna is formed having a first element driven by a transceiver, a second element connected to ground wherein the second element overlaps with the first element to form a capacitive coupling region, and a third element. The third element can be either driven or grounded and overlaps with at least one of the first element and the second element. Each overlapping region between the first, second and third elements creates a capacitive coupling region forming a resonant frequency, wherein the resonant frequency is adjusted by the amount of overlap and the bandwidth is determined by the separation distance between the overlapping elements. In this embodiment, an overlapping region can be formed between the driven element and a grounded element, or alternatively the overlapping region can be formed between two grounded elements.

In another embodiment, the grounded elements are parallel to the driven element. Alternatively, the grounded elements can be orthogonal with respect to the driven element. One or more elements can comprise an active tuning component. The active tuning component can be configured within or near a ground plane. Alternatively, one or more active components can be configured on an antenna element. One or more antenna elements can be bent. One or more antenna elements can be linear, or planar. One or more antenna elements can be fixedly disposed above a ground plane. Alternatively, one or more antenna elements can be configured within a ground plane.

In another embodiment, an antenna is provided having a high band radiating element and a low band radiating element. A switched network can be integrated with at least one of the high band or low band radiating elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary isolated magnetic dipole (IMD) antenna comprised of a first element attached to a transmitter and coupled to a second element which is connected to ground.

FIG. 2 shows a plot of return loss as a function of frequency for the IMD antenna in FIG. 1. A single resonance is present.

FIG. 3 illustrates an isolated magnetic dipole (IMD) antenna comprised of a first element attached to a transmitter and coupled to a second element which is connected to ground along with a third element which is coupled to the second element.

FIG. 4 shows the return loss as a function of frequency for the antenna shown in FIG. 3. A second resonance is present which is formed by the addition of the third element.

FIG. 5 illustrates an IMD antenna with two additional elements, a third and fourth, each coupled to the second element of the IMD antenna.

FIG. 6 illustrates an isolated magnetic dipole (IMD) antenna comprised of an element attached to a transmitter and coupled to a second element which is connected to ground along with a third element which is coupled to the first element.

FIG. 7 illustrates an IMD antenna with two additional elements, a third and fourth, each coupled to the first element of the IMD antenna.

FIG. 8 illustrates an isolated magnetic dipole (IMD) antenna comprised of a first element attached to a transmitter and coupled to a second element which is connected to ground along with a third element which is coupled to the second element. A component is connected between the third element and ground.

FIG. 9 illustrates an isolated magnetic dipole (IMD) antenna comprised of a first element attached to a transmitter and coupled to a second element which is connected to ground along with a third element which is coupled to the first element. A component is connected between the third element and ground.

FIG. 10 illustrates an IMD antenna with two additional elements, a third and fourth, each coupled to the second element of the IMD antenna. A component is connected between the third element and ground, with another component connected between the second element and ground.

FIG. 11 illustrates an IMD antenna with an additional element coupled to the second element of the IMD antenna. The additional element is configured in a 3-dimensional shape and is not restricted to a plane containing the first two elements.

FIG. 12 illustrates an IMD antenna with two additional elements, a third and fourth, with the third element coupled to the second element and the fourth element coupled to the first element. Both the third and fourth elements are bent in 3 dimensional shapes and are not restricted to a plane containing the first two elements. A component is connected between the fourth element and ground.

FIG. 13 illustrates an IMD antenna with two additional elements, a third and fourth, with a component connecting two portions of the third element.

FIG. 14 illustrates an IMD antenna with two additional elements, a third and fourth, with a component connecting the third and fourth elements.

FIG. 15 illustrates an IMD antenna with two additional elements, a third and fourth, with all four elements positioned in the plane of the ground plane.

FIG. 16 illustrates an antenna configuration where a switch network is integrated into the low band radiating element to provide a tunable antenna. The switch network can be implemented in a MEMS process, integrated circuit, or discrete components.

FIG. 17 illustrates an antenna configuration where a switch network is integrated into the high band radiating element to provide a tunable antenna. The switch network can be implemented in a MEMS process, integrated circuit, or discrete components.

FIG. 18 illustrates an antenna configuration where switch networks are integrated into the low band and high band radiating elements to provide a tunable antenna. The switch networks can be implemented in a MEMS process, integrated circuit, or discrete components.

FIG. 19 illustrates an antenna implementation of the concept described in FIG. 3. A driven element is coupled to two additional elements, resulting in a low band and high band resonance.

FIG. 20 shows the return loss of the antenna configuration shown in FIG. 19. The two traces refer to two capacitor values for component loadings of the second element. The capacitor is not shown in FIG. 19.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, for purposes of explanation and not limitation, details and descriptions are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from these details and descriptions.

Embodiments of the present invention provide an active tuned loop-coupled antenna capable of optimizing an antenna over incremental bandwidths and capable of tuning over a large total bandwidth. The active loop element is capable of serving as the radiating element or an additional radiating element may also be coupled to this active loop. In various embodiments, multiple active tuned loops can be coupled together in order to extend the total bandwidth of the antenna. Such active components may be incorporated into the antenna structure to provide further extensions of the bandwidth along with increased optimization of antenna performance over the frequency range of the antenna.

In a primary embodiment, the invention includes a first element and a second element positioned above a ground plane. The first and second element can be wire, or preferably a planar element. The first element is connected to a transceiver. The second element is connected to ground and at least partially overlaps with the first element to form a first coupling region. The coupling region is defined by the amount of overlap between the first and second elements, and the distance between the first and second elements. The coupling region can include a capacitive coupling between two antenna elements. By adjusting the amount of overlap and the distance between the elements, one can adjust the frequency and bandwidth of the antenna. A third element connected to ground is further positioned near at least one of the first element and the second element. The third element can form a second coupling region when placed near one of the first element or the second element, thus creating a second resonant frequency for which the antenna is operational. Optionally, the third element can be placed within the vicinity of the first and second elements, thereby further generating a third coupling region. Any number of subsequent elements can be positioned near an antenna element to create a coupling region.

In a preferred embodiment, each of the antenna elements are planar elements and are substantially parallel to the ground plane. In certain embodiments, the antenna elements are not parallel with the ground plane. Other embodiments are described below in more detail.

FIG. 1 illustrates a driven element 1, and a capacitively coupled element 2 that is grounded forming an inductive loop. The coupling region 3 between elements 1 and 2 forms a single resonant frequency from the combined structure. The resonant frequency is adjusted by the amount of overlap of the two elements. The separation between the two elements determines the bandwidth of the resonance.

FIG. 2 illustrates a plot of frequency vs. return loss showing the effect of coupling a driven element and one capacitively coupled element that is grounded. A single resonant frequency is shown.

FIG. 3 illustrates a driven element 20, and two capacitively coupled elements 21 and 22 that are grounded forming inductive loops. The coupling 23 between elements 20 and 21, and the coupling 24 between 21 and 22 produces two resonant frequencies each determined by the amount of overlap and separation between the two elements. The separation between the elements determines the bandwidth for each resonance.

FIG. 4 illustrates a plot of frequency vs. return loss showing the effect of coupling a driven element and two capacitively coupled elements. Two resonate frequencies are shown.

FIG. 5 illustrates a driven element 30, and three capacitively coupled elements 31, 32 and 33 that are grounded forming inductive loops. The coupling 34 between elements 30 and 32, the coupling 35 between 31 and 32 and coupling 36 between 32 and 33 produces three resonant frequencies each determined by the amount of overlap and separation between the three elements. The separation between the elements determines the bandwidth for each resonance.

FIG. 6 illustrates a driven element 40, and two capacitively coupled elements 41 and 42 that are grounded forming inductive loops. The positioning of the elements creates an overlapping between the elements that forms three couplings 43, 44 and 45. The separation between the elements determines the bandwidth for each resonance.

FIG. 7 illustrates a driven element 50, and four capacitively coupled elements 51, 52, 53 and 54 that are grounded forming inductive loops. The positioning of the elements creates an overlapping between the elements that forms four couplings 55, 56, 57 and 58. The separation between the elements determines the bandwidth for each resonance.

FIG. 8 illustrates a driven element 60 with one capacitively coupled element 61 that is connected to ground forming an inductive loop and a coupling region 65. The frequency response generated by this coupling region 65 will be dependent upon the amount of overlap and separation distance of the elements 60 and 61. A second coupled element 62 is connected to ground via a component 63. If this component is passive (inductor, capacitor, resistor) it will create a fixed frequency response from the coupling region 64. If the component is tunable (tunable capacitor, varactor diode, etc.) then the frequency response can be dynamically tuned (in real time).

FIG. 9 illustrates a driven element 70 with one capacitively coupled element 72 that is connected to ground forming an inductive loop and a coupling region 75. The frequency of this coupling region 75 will be dependent upon the amount of overlap and separation distance of the elements 70 and 72. The driven element 70 is also coupled to a second element 71 that is connected to ground via a component 73. If this component is passive (inductor, capacitor, resistor) it will create a fixed frequency response from the coupling region 76. If the component is tunable (tunable capacitor, varactor diode, etc.) then the frequency response can be dynamically tuned (in real time). Element 71 is also coupled to element 72 and will have a fixed or dynamically tuned frequency response, dependent on the type and value of component 73.

FIG. 10 illustrates a driven element 80 coupled to a second element 81 that is connected to ground via a component 86. If this component is passive (inductor, capacitor, resistor) it will create a fixed frequency response from the coupling region 76. If the component is tunable (tunable capacitor, varactor diode, etc.) then the frequency response can be dynamically tuned (in real time). Element 81 forms a coupling 87 with element 84 that is connected to ground. The frequency of this coupling region 87 will be dependent upon the amount of overlap and separation distance of the elements 81, 84 and the driven element 80. Another coupling region 89 is formed by elements 81 and 82. Both elements are connected to ground by components 85 and 86.

FIG. 11 illustrates a driven element 90 with one capacitively coupled element 91 that is connected to ground forming an inductive loop and a coupling region 93. An additional coupling is formed between capacitively coupled elements 91 and 92. The frequency of this coupling region 94 will be dependent upon the amount of overlap and separation distance of the elements 91 and 92 and driven element 90.

FIG. 12 illustrates a driven element 100 with a capacitively coupled element 102 that is connected to ground forming an inductive loop and coupling region 106. Element 102 is capacitively coupled to element 103 that is connected to ground forming an inductive loop and coupling region 105. Element 103 is bent in a 3 dimensional shape and is not restricted to a plane containing the other elements. The driven element 100 is also coupled to a second element 101 that is connected to ground via a component 104 forming a coupling region 107 with driven element 100. If the component 104 is tunable (tunable capacitor, varactor diode, etc.) then the frequency response can be dynamically tuned (in real time). Element 101 is bent in a 3 dimensional shape and is not restricted to a plane containing the other elements.

FIG. 13 illustrates a driven element 200 in-line with element 201 that is connected to ground. The driven element 200 is coupled to a second element 202 that is connected to ground via a component 204 forming a coupling region 207 with driven element 200. If the component 204 is tunable (tunable capacitor, varactor diode, etc.) then the frequency response can be dynamically tuned (in real time). Element 202 also forms a coupling 209 with element 203 that is grounded via a component 205. In addition element 203 has a component 206 that connects the two parts of element 203 further extending frequency tuning and response.

FIG. 14 illustrates a driven element 300 in-line with element 301 that is connected to ground. The driven element 300 is coupled to a second element 302 that is connected to ground via a component 304 forming a coupling region 309 with driven element 300. If the component 304 is tunable (tunable capacitor, varactor diode, etc.) then the frequency response can be dynamically tuned (in real time). Element 302 also forms a coupling 308 with element 301 that is connected to ground forming an inductive loop. A further coupling is formed between element 302 and element. A component 306 is connected to elements 302 and 303, providing additional tuning of the frequency response.

FIG. 15 FIG. 12 illustrates a driven element 400 with capacitively coupled elements 401, 402 and 403 that are connected to the edge of a ground plane producing three couplings 404, 405 and 406 respectively.

FIG. 16 illustrates an antenna configuration where a switch network 500 is integrated into the low band radiating element 501 to provide a tunable antenna. The switch network can be implemented in a MEMS process, integrated circuit, or discrete components.

FIG. 17 illustrates an antenna configuration where a switch network is integrated into the high band 600 radiating element to provide a tunable antenna. The switch network 601 can be implemented in a MEMS process, integrated circuit, or discrete components.

FIG. 18 illustrates an antenna configuration where switch networks are integrated into the low band 700 and high band 702 radiating elements to provide a tunable antenna. The switch networks 701 and 703 can be implemented in a MEMS process, integrated circuit, or discrete components.

FIG. 19 illustrates antenna implementation of the concept described in FIG. 3. A driven element 720 is coupled to two additional elements, 721 and 722, resulting in a low band and high band resonance.

FIG. 20 illustrates a plot of frequency vs. return loss for the antenna described in FIG. 19. The two traces refer to two capacitor values for a component loading element 721. 

1. An antenna, comprising: a first element and a second element positioned above a ground plane, said first element connected to a transceiver, said second element connected to ground and coupled to said first element to form a first coupling region, and a third element positioned above the ground plane, said third element connected to ground and coupled to at least one of the first element and second element to form a second coupling region.
 2. The antenna of claim 1, comprising four or more elements, said four or more elements including at least one driven element, wherein each element is coupled to at least one of a driven element and a grounded element.
 3. The antenna of claim 1, wherein at least one of the second element or the third element is connected to ground by a component for varying the frequency of the antenna.
 4. The antenna of claim 3, wherein said component is one of a capacitor, inductor, resistor, diode, active tuning component, or a switch.
 5. The antenna of claim 4, comprising multiple components.
 6. The antenna of claim 1, wherein said first element and said second element are configured to form an Isolated Magnetic Dipole (IMD) element.
 7. The antenna of claim 6, wherein the IMD element comprises a first portion connected the transceiver and a second portion coupled to the first portion.
 8. The antenna of claim 7, wherein the third element is connected to the ground plane at one end and coupled to the first portion of the IMD element.
 9. The antenna of claim 8, wherein multiple elements are coupled to the IMD element at the first portion.
 10. The antenna of claim 9, wherein at least one element is connected to a component selected from the group consisting of: a capacitor, inductor, resistor, diode, active tuning component, and a switch.
 11. The antenna of claim 10, wherein said component is connected to ground. 